Faculty Bibliography

The aim of this study was to clinically evaluate the guided bone regeneration (GBR) potential of allograft, xenograft, and alloplastic materials in combination with resorbable membranes in extraction sockets. The qualitative and quantitative assessments of this prospective study were accomplished through histologic and histomorphometric analysis. Three experimental groups and 1 control group for comparison (n = 8) received either an allograft (human cancellous bone, freeze dried, Deutsches Institut für Zell und Gewebeersatz, Berlin, Germany), xenograft (BioOss, Geistlich Pharma AG, Wolhusen, Switzerland), or alloplast (biphasic calcium sulphate, Bondbone, MIS Implants Technologies Ltd., Charlotte, NC). The negative control group received no regenerative material. Tissue samples were then qualitatively and quantitatively evaluated as a function of percentage of new vital bone, graft particles content, soft tissue, and bone marrow over time. All 3 study groups presented bone volume suitable for the successful placement of a dental implant. The xenograft group yielded significantly less amount of vital bone compared with the allograft and alloplast groups. When comparing the percentage of residual graft particles, there was significantly greater amounts associated with the xenograft group in contrast to the allograft and alloplast groups. Similarly, a significantly increased amount of soft tissue percentage was observed within the xenograft group relative to all other groups. No significant differences were observed in the percentage of residual graft particles between the allograft and alloplast groups. There were also no significant differences detected in vital bone percentage between the allograft, alloplast, and control groups. When evaluating the bone marrow percentage, the only significant difference detected was between the xenograft and alloplast materials. Overall, no complications (ie, fever, malaise, purulence or fistula) were observed during the entirety of clinical trial among all patients. The greatest GBR potential was associated with the allograft material because of the greater degree of vital bone and the lowest percentage of residual graft particles. All studied bone substitute materials resulted in bone apposition for efficient use in alveolar ridge preservation procedures.

To evaluate the effect of fatigue and aging on the crystalline content and reliability of a zirconia-toughened-alumina (ZTA) composite compared to its individual counterpart materials (3Y-TZP and Al₂O₃). Thirty-six disc-shaped specimens per group were obtained to comply with ISO 6872:2015. Crystalline content, microstructure and reliability of experimental groups were evaluated in four stages: 1) immediate; 2) aged; 3) fatigued; 4) aged + fatigue. Aging was performed in autoclave and Step-Stress-Accelerated-Life-Testing (SSALT) was performed using three stress profiles. Weibull statistics were used to determine Weibull parameters and life-expectancy. A significant increase in monoclinic phase in 3Y-TZP was observed after aging (19.31%), fatigue (17.88%) and aging + fatigue (55.81%), while ZTA evidenced minimal variation among all conditions (<5.69%). 3Y-TZP presented higher reliability than ZTA at 300 and 500 MPa, and ZTA outperformed Al₂O₃ at the same stress missions. None of the ceramics yielded acceptable reliability at 800 MPa. A higher characteristic strength was observed for 3Y-TZP, followed by ZTA and Al₂O₃. While after aging ZTA and Al₂O₃ remained stable, 3Y-TZP exhibited a significant increase in the characteristic stress. Aging did not affect the reliability of ZTA and Al₂O₃. 3Y-TZP demonstrated an increase in monoclinic content and characteristic strength after aging.

Fused Filament Fabrication (FFF)-based 3D printing is an efficient technique for developing medical implants, but it is not very useful in developing small yet mechanically robust design-specific fixtures such as dental implants (<15 mm). Specifically, it is challenging to 3D print robust Polyetheretherketone (PEEK) small implants due to PEEK's high melting temperature and melt viscosity. However, in this study, we efficiently utilize high-temperature FFF to develop the first-of-its-kind patient-specific robust PEEK dental implants with high print resolution. Specifically, we explore the effects of critical FFF processing conditions on the mechanical properties of the implants and subsequently determine an optimized set of processing conditions that are essential in developing durable dental implant systems. Our results indicate that the 3D printed dental implants exhibit good fatigue properties and suffice the clinical and industrial requirements for dental implants. Furthermore, we prove that the 3D printed implants exhibit adequate mechanical durability even after simulated (accelerated) aging of 30 years.

PURPOSE/OBJECTIVE:This study evaluated the probability of survival and failure mode of endodontically treated incisors without ferrule restored with CAD/CAM FRC post-cores. METHODS:Root canals of bovine incisors were treated, leaving post preparations of ∼10 mm. Teeth were allocated into three groups: (i) cast metal post-core, (ii) FRC prefabricated post with a direct resin core build-up, and (iii) CAD/CAM FRC post-core. Posts and zirconia crowns were cemented using resin cement. Specimens were subjected to step-stress accelerated-life fatigue testing in water. Use level probability Weibull curves, probability of survival for a mission of 100,000 cycles at 25, 50, and 100 N, Weibull modulus, and characteristic strength were calculated and plotted. Failure mode was examined under a stereomicroscope. RESULTS:Restored incisors demonstrated high probability of survival (93-100%) for missions estimated at 25 and 50 N, irrespective of post-core foundation. At 100 N, incisors restored with metal posts presented significantly higher probability of survival (99%) relative to CAD/CAM posts (79%), whereas FRC groups demonstrated no significant difference. Weibull analysis indicated no significant difference on the Weibull modulus (m = 3.38-5.92). Incisors reconstructed with metal post-cores (431 N) presented significantly higher characteristic strength relative to prefabricated (200 N) and CAD/CAM (202 N) FRC post-cores. While post fracture was the chief failure mode for prefabricated and CAD/CAM FRC post-cores, post and/or root fracture were the main event for metal post-cores. CONCLUSION/CONCLUSIONS:Endodontically treated incisors without ferrule restored with CAD/CAM FRC post-cores presented promising probability of survival for loads compatible with anterior masticatory forces and favorable failure modes.

The identification of ancient worked materials is one of the fundamental goals of lithic use wear analysis and one of the most important parts of understanding how stone tools were used in the past. Given the documented overlaps in wear patterns generated by different materials, it is imperative to understand how individual materials' mechanical properties might influence wear formation. Because isolating physical parameters and measuring their change is necessary for such an endeavor, controlled (rather than replicative) experiments combined with objective measurements of surface topography are necessary to better grasp how surface modifications formed on stone tools. Therefore, we used a tribometer to wear natural flint surfaces against five materials (bone, antler, beech wood, spruce wood, and ivory) under the same force, and speed, over one, three, and five hours. The study aimed to test if there is a correlation between surface modifications and the hardness of the worked material. We measured each raw material's hardness using a nano-indentation test, and we compared the surface texture of the flint bits using a 3D optical profilometer. The interfacial detritus powder was analyzed with a scanning electron microscope to look for abraded flint particles. We demonstrate that, contrary to expectation, softer materials, such as wood, create a smoother surface than hard ones, such as ivory.

BACKGROUND:We aimed to histomorphometrically evaluate the effects of Leucocyte-Platelet-Rich Fibrin (L-PRF), with and without the combination of a bone grafting material, for alveolar ridge preservation using an in vivo canine model. MATERIAL AND METHODS/METHODS:Seven dogs (Female Beagles, ~18-month-old) were acquired for the study. L-PRF was prepared from each individual animal by drawing venous blood and spinning them through a centrifuge at 408 RCF-clot (IntrasSpin, Intra-Lock, Boca Raton, FL). L-PRF membranes were obtained from XPression fabrication kit (Biohorizons Implant Systems, Inc., AL, USA). A split mouth approach was adopted with the first molar mesial and distal socket defects treated in an interpolated fashion of the following study groups: 1) Empty socket (negative control); 2) OSS filled defect 3) L-PRF membrane; and 4) Mix of Bio-Oss® with L-PRF. After six weeks, samples were harvested, histologically processed, and evaluated for bone area fraction occupancy (BAFO), vertical/horizontal ridge dimensions (VRD and HRD, respectively), and area of coronal soft tissue infiltration. RESULTS:BAFO was statistically lower for the control group in comparison to all treatment groups. Defects treated with Bio-Oss® were not statistically different then defects treated solely with L-PRF. Collapsed across all groups, L-PRF exhibited higher degrees of BAFO than groups without L-PRF. Defects filled with Bio-Oss® and Bio-Oss® with L-PRF demonstrated greater maintenance of VRD relative to the control group. Collapsed across all groups, Bio-Oss® maintained the VRD and resulted in less area of coronal soft tissue infiltration compared to the empty defect. Soft tissue infiltration observed at the coronal area was not statistically different among defects filled with L-PRF, Bio-Oss®, and Bio-Oss® with L-PRF. CONCLUSIONS:Inclusion of L-PRF to particulate xenograft did not promote additional bone heading at 6 weeks in vivo. However, we noted that L-PRF alone promoted alveolar socket regeneration to levels comparable to particulate xenografts, suggesting its potential utilization for socket preservation.

Leukocyte-platelet-rich fibrin (L-PRF) has been suggested for gap management for immediate implant placement when the distance is greater than 2 mm. However, there remains a paucity in hierarchically designed research to support this application. The present study aimed to evaluate the effect of L-PRF on the osseointegration parameters of dental implants placed after conventional osteotomy of surgically created bone defects that simulate post extraction sockets in a canine model after 3, 6, and 12 weeks in vivo. Eighty dental implants (Intra-Lock, Boca Raton, FL) were placed in the radius of 13 beagle dogs. The experiment consisted of 4 groups (n = 20 implants/group): 1) Regular osteotomy (Reg n/L-PRF); 2) Regular osteotomy and implant placement with L-PRF membrane (Reg L-PRF); 3) Wide osteotomy with no gap management performed, where an osteotomy/bony defect (6 mm of diameter and ~5 mm deep) was created to simulate immediate implant placement in post-extraction sockets, and the gap was left for spontaneous healing (Wide nL-PRF); and 4) Wide osteotomy with L-PRF gap management (Wide L-PRF). L-PRF membranes were obtained by blood drawn from each subject and centrifuged at 2700 rpm (408 RCF-clot) for 12 min. In the experimental groups where L-PRF was utilized, the membrane was inserted into the osteotomy site prior to implant placement. Six dogs had implants placed in the radius for 3 weeks; and 7 dogs had implants placed in the left radius for 6 weeks and in the right radius for 12 weeks. At the corresponding experimental time points, samples were harvested, and subjected to histological processing for qualitative and quantitative analyses, via bone-to-implant contact (BIC) and bone-area-fraction occupancy (BAFO). Qualitative analysis demonstrated increased amounts of bone formation around the implant and within the healing chambers over time for all groups. While comparable histological features were observed for both Reg groups (L-PRF and nL-PRF), the gap management performed in Wide L-PRF group resulted in effective gap filling with improved bone growth in close proximity to the implant surface. Quantitative analyses of BIC and BAFO yielded higher values for both variables at 3 weeks for Wide L-PRF (~38% and ~56% respectively) compared to Wide nL-PRF (~20% for BIC and BAFO) (p < .03). No statistical differences were detected between Wide groups at 6 and 12 weeks, neither between Reg groups, independent of the association with or without the L-PRF membrane at all healing times. L-PRF placed within wide osteotomies, prior to implant placement, resulted in increased early bone formation compared to unfilled wide osteotomies at the early healing time (3 weeks in vivo).

The aim of this study was to evaluate the in vivo performance of two different deproteinized bovine bone (DBB) grafting materials: DBBB (Bio-Oss®) and DBBL (Laddec®), for the regeneration of critically sized (8 mm) defects in rabbit's calvaria. Three round-shaped defects were surgically created in the calvaria of 13 New Zealand White rabbits proximal to the coronal suture in the parietal bone. Two of the defects were filled with one of the grafting materials while a third was left empty to serve as a negative control. Bone regeneration properties were evaluated at 4- and 8-weeks after implantation by means of histological and histomorphometrical analyses. Statistical analyses were performed through a mixed model analysis with fixed factors of time and material. Histological evaluation of the control group evidenced a lack of bridging bone formation across the defect sites at both evaluation time points. For the experimental groups, new bone formation was observed around the defect periphery and to progress radially inwards to the center of the defect site, regardless of the grafting material. Histomorphometric analyses at 4 weeks demonstrated higher amount of bone formation through the defect for DBBB group. However, at 8 weeks, DBBL and DBBB demonstrated osteoconductivity and low resorption rates with evidence of statistically similar bone regeneration through the complete boney defect. Finally, DBBB presented lower soft tissue migration within the defect when compared to DBBL at both evaluation time points. DBBB and DBBL presented similar bone regeneration performance and slow resorption rates. Although both materials promoted bone regeneration through the complete defect, DBBB presented lower soft tissue migration within the defects at 4- and 8-weeks.

PURPOSE/OBJECTIVE:To evaluate the effect of composition, fabrication mode, and thermal cycling on the mechanical properties of different polymeric systems used for temporary dental prostheses. MATERIALS AND METHODS/METHODS:Standard bar-shaped specimens (25 × 2 × 2 mm) were fabricated of six polymeric systems of varying compositions and fabrication modes (n = 10/group): conventional PMMA (Alike, GC) - group CGC; conventional PMMA (Dêncor, Clássico) - group CD; bis-acryl (Tempsmart, GC) - group BGC; bis-acryl (Yprov, Yller) - group BY; milled PMMA (TelioCAD, Ivoclar) - group MI; 3D printed bis-acryl - (Cosmos Temp, Yller) group PY. Half of the specimens were subjected to 5000 thermal cycles (5 °C to 55 °C). Three-point bending tests were performed using a universal testing machine with a crosshead speed set to 0.5 mm/min. Flexural strength and elastic modulus were calculated from the collected data. FTIR spectra were recorded pre and post curing and after thermal cycling to evaluate material composition and degree of conversion. Energy-dispersive spectroscopy (EDS) and scanning electron microscope (SEM) were utilized to examine the composition and micromorphology of the systems, respectively. Data were analyzed using two-analysis of variance and Tukey tests (α = 0.05). RESULTS:FTIR spectra indicated that BGC, BY and PY groups corresponded to urethane dimethacrylate systems (bis-acryl), while CGC, CD, and MI groups corresponded to monomethacrylate systems, polymethyl methacrylate (PMMA). Bis-acryl BGC system yeilded the highest flexural strength (80 MPa), followed by the milled PMMA MI system (71 MPa), both statistically significant different relative to other groups. Bis-acryl BY exhibited the lowest flexural strength (27 MPa). Thermocycling significantly increased the flexural strength of all polymeric systems (∼10-15 MPa), except for the 3D-printed PY group. Bis-acryl BGC (1.89 GPa) and conventional PMMA CGC (1.66 GPa) groups exhibited the highest elastic modulus, followed by milled PMMA MI group (1.51 GPa) and conventional PMMA CD (1.45 GPa) systems, with significant difference detected between BGC group and MI and CD groups. The 3D printed PY (0.78 GPa) and bis-acryl BY (0.47 GPa) systems presented the lowest elastic modulus. Thermocycling did not have a significant influence on the elastic modulus. FTIR spectra indicate water sorption and release of unreacted monomers as well as increased degree of conversion (∼5-12%) after thermal cycling. CONCLUSION/CONCLUSIONS:Composition and fabrication mode and thermal cycling significantly affected the mechanical properties of polymeric systems used for temporary dental prostheses.